With the exponentially increasing usage of Kotlin these days, many developers face the issue of how to test the newly created Kotlin classes. As we know all classes and methods are final be default in Kotlin, unless specifically open-ed. Unfortunately Mockito, one of the most popular mocking libraries for Java projects, can’t easily mock final classes. Since we don’t want to open up everything just for testing purposes, we need another solution.

Hadi Hariri highlighted in his excellent blog post that Mockito version 2.1.0 and above can perform the magic of mocking final classes. Since mocking is something used only in tests … and usually it just works, we’ve neglected Mockito and were still using a very outdated version (1.10.19) in our project. There were a few pain-points while updating to the latest one, so hopefully this post will save you some time when going through the same process.read more